Radio frequency identification (RFID) is the wireless use of electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects. The RFID tags may contain information electronically stored therein. Some tags are powered by electromagnetic induction from magnetic fields produced near the reader. Some types collect energy from the interrogating radio waves and act as a passive transponder. Other types have a local power source such as a battery and may operate at hundreds of meters from the reader. Unlike a barcode, the tag does not necessarily need to be within line of sight of the reader and may be attached to or embedded in the tracked object.
RFID tags have been widely used. For example, an RFID tag attached to an automobile during production can be used to track its progress through the assembly line; RFID-tagged pharmaceuticals can be tracked through warehouses; and implanting RFID microchips in livestock and pets allows positive identification of animals. In most cases, the behavior pattern between the tags and reader is single and defined in advance. As used herein, the behavior pattern defines one or more actions to be done when the reader identifies the tag. For example, in a warehouse, the stock size is modified once the reader receives identification data sent by the certain type of RFID tags. There are also some kinds of tags that work with different communication channels but with the same or similar principle of operations.